TORONTO — A 100-pound python blamed in the strangling deaths of two Canadian boys apparently escaped from its enclosure, slithered through a ventilation system and fell through the ceiling into the room where the young brothers were sleeping, authorities said Tuesday.

A snake expert said it was possible that the python was spooked and simply clung to whatever it landed on. Police are treating the deaths in Campbellton, New Brunswick, as a criminal investigation.

Autopsies on Noah Barthe, 4 and his brother Connor Barthe, 6, were performed Tuesday.

The brothers had been visiting the apartment of a friend whose father owned an exotic pet store on the floor below, Royal Canadian Mounted Police Sgt. Alain Tremblay said at a news conference in Campbellton. Tremblay said the African rock python was being kept inside the second floor apartment, not inside the pet store as authorities had previously stated.

Steve Benteau, a spokesman for the provincial Natural Resources Department, said no permit was issued for an African rock python and provincial authorities weren’t aware it was being kept at the apartment. The department said the snake is generally only permitted in accredited zoos, unless there is a special permit.

Tremblay said the snake was housed in a large glass enclosure that reached the ceiling of the apartment and escaped through a small hole in the ceiling connected to the ventilation system. He said the snake made its way through the ventilation system and moved toward the living room, where the boys were sleeping. The pipe collapsed and the snake fell.

The friend of the boys was sleeping in another room and was unharmed.

The pet store owner, Jean-Claude Savoie, told the Global News television station that he didn’t hear a sound and discovered the “horrific scene” when he went into his living room on Monday morning.

“I can’t believe this is real,” Savoie said.

He said the boys were the children of his best friend and were often at his apartment to visit his son. Savoie said the python, which he has had for at least 10 years, had been kept alone in its enclosure and was not handled by anyone else.

Police said the snake was killed by a veterinarian. It was sent for a necropsy to confirm the type of snake and help understand what may have caused it to attack.